There are thousands of patients in China suffering severe coronary atherosclerotic heart diseases who need a percutaneous transluminal coronary angioplasty (PTCA) and a stent placement annually. However, 30% of the patients subject to such operations will be faced with the problem of narrowing of blood vessels within half a year. After blood vessel dilation operations, these patients will generate many cells that block blood vessels due to failure in normal rehabilitation. As a result, they need one more bypass grafting operation or angioplasty.
In recent years, a new method capable of inhibiting cell division is invented in the medical circle, i.e., a drug eluting stent, which coats the stent for dilating blood vessels of a patient with a medicament that releases an antibiotic capable of inhibiting growth of abnormal cells. Thus, the blood vessels will not be blocked by cells and thereby will not become narrow.
Usually, the drug eluting stent carries a medicament via a polymer coated on the surface of a bare metal stent. When the stent is implanted into a lesion site within a blood vessel, the medicament releases controllably in a manner of eluting from the polymer coating into cardiovascular wall tissue to exert biological effect. At present, for most existing drug eluting stents, usually an active medicament and a polymer are mixed and coated on the partial or entire surface of the bare stent. In clinic application, such medicament stent having a polymer coating can reduce the incidence of narrowing again to below 10%. However, such drug eluting stent possibly leads to formation of a thrombus after being implanted into a human body due to a continuous decrease in the medicament and a correspondingly continuous increase in the polymer concentration.
Accordingly, the existing technology puts forward a nanoscale aperture releasing architecture for a drug eluting stent, which opens the drug eluting stent with a plurality of nanoscale apertures thereon to effectively control the medicament release rate and reduce the risk of incurring a thrombus after implantation of the drug eluting stent into human body tissues. But such architecture needs to coat the nanoscale apertures with a traditional method, such as a coating method etc. The defect of the method lies in failure in precisely loading a desirable part with a medicament. Especially for a stent with rather small grooves or holes for being loaded with a medicament, it is more difficult for the traditional method to precisely identify and locate positions of the grooves, and thus unable to provide bases for medicament loading processes.
Besides, in the known technology, a large amount of non-deformable small apertures capable of storing a medicament, which are called medicament storage grooves are processed on the surface of a bare metal stent. These storage grooves can provide medicament eluting, whereby it is not necessary any more for a medicament to be coated on the stent surface but to be buried in the storage grooves together with a biodegradable polymer. Such technology can realize a positional release of medicament, and has higher precision. Such manner can control not only the medicament eluting time but also the medicament eluting rate.
However, the bare metal stent with medicament storage grooves is formed from etching a tube with a laser technique. The processed bare metal stent will undergo a displacement of actual positions of the medicament storage grooves in relative to theoretical designed positions caused by the elastic deformation of itself and the process of manual pickup and placement. Since the medicament grooves have very small dimensions, usually about 20 to 80 microns, if a dispensing device still performs the dispensing operation at the designed position, the medicament will be dispensed outside the grooves. After the stent is implanted into a human body, the medicament formed outside the grooves will peel off the stent, thereby causing formation of a thrombus.